1
UD UD UD SHADY RILL FAULT DOG RIVER FAULT ZONE SHADY RILL FAULT DOG RIVER FAULT ZONE RICHARDSON MEMORIAL CONTACT U D T T T T T T T T T T T T T T T T T T Biotite Garnet Biotite Garnet Garnet Biotite 4A 4B 5A, B 6A 6B 19D 10A 10B 10C 10D 10E 10F, 14B 12C, D 13B 13C 13D 15B 15C 17A 17B 19A 19B 19C 6E 14294 14293 No. 7 14300 14300 71 71 74 68 86 62 78 74 77 61 70 76 50 52 71 82 79 76 79 79 58 15 71 47 72 54 72 49 63 65 70 79 60 65 74 80 63 76 66 67 68 71 84 61 76 64 63 64 74 65 74 78 74 64 71 85 76 74 65 64 76 42 21 71 51 75 52 35 72 71 72 78 32 10 22 72 80 72 80 82 62 74 51 75 60 84 52 67 76 74 70 48 84 51 70 55 66 28 56 37 72 64 67 72 81 87 79 55 44 72 70 52 71 77 50 87 81 82 77 54 74 71 57 78 58 74 18 30 71 68 63 81 72 67 42 51 81 51 88 59 68 76 86 44 73 86 59 88 87 68 68 18 87 80 71 81 44 71 44 81 13 16 24 54 67 35 36 82 79 58 76 81 25 46 76 81 82 82 85 82 75 85 68 54 51 80 44 79 39 68 74 55 39 46 10 86 74 74 42 84 78 17 72 56 25 52 86 57 65 9 86 63 66 78 49 81 65 50 32 26 36 32 32 15 70 68 16 66 80 78 75 35 76 32 22 80 71 35 66 66 76 76 25 49 36 72 48 29 75 37 81 28 40 65 69 79 50 74 74 81 78 70 71 77 62 19 24 49 69 30 28 68 64 78 67 72 46 88 34 21 59 76 71 68 25 58 34 39 71 80 57 82 89 62 74 58 40 21 58 47 79 55 88 39 74 44 76 48 86 48 41 56 36 78 49 1 12 76 41 76 74 33 55 75 74 45 67 73 76 25 79 34 64 25 69 59 81 76 67 59 74 41 37 67 24 31 62 35 65 43 56 41 59 66 26 10 66 80 61 69 55 80 49 37 70 72 71 58 70 74 74 49 44 55 69 22 50 52 71 78 46 31 64 88 64 61 43 31 56 63 68 72 34 74 62 43 63 53 45 44 66 54 75 38 75 47 66 15 22 60 34 70 37 41 71 58 71 64 64 60 65 32 50 84 84 56 62 43 35 65 22 55 55 74 27 66 62 64 78 65 26 17 67 44 45 44 72 41 54 70 57 73 30 62 80 82 68 43 41 58 54 82 43 48 37 67 72 59 30 57 36 61 66 70 44 47 35 68 27 28 76 38 48 34 36 66 71 55 58 56 69 89 75 56 54 26 58 71 78 70 81 17 15 70 5 70 46 41 89 82 48 48 48 58 27 59 5 64 48 68 62 66 61 66 47 76 43 59 26 35 59 22 29 17 82 74 40 74 27 41 29 45 63 58 31 36 74 68 34 39 18 51 68 64 31 68 65 70 36 29 51 24 20 67 27 38 49 40 51 72 41 51 24 26 45 40 66 64 32 50 21 54 40 55 42 55 52 42 26 70 20 39 47 29 41 68 48 72 64 34 43 24 54 42 31 68 56 58 30 51 40 51 24 40 38 42 58 33 45 16 25 29 41 78 59 37 34 28 28 47 66 4 12 65 57 24 31 26 42 48 36 74 42 34 48 33 67 31 28 49 26 21 21 16 30 32 28 6 50 2 49 59 26 22 47 48 51 67 40 45 28 38 64 24 70 12 57 51 64 59 68 68 65 67 54 55 54 38 68 66 65 59 65 32 56 16 54 30 40 61 43 66 62 61 44 19 48 58 58 54 45 36 10 20 32 55 24 21 30 42 17 74 28 67 23 25 45 62 4 59 54 47 66 53 74 16 16 41 41 28 57 42 29 28 55 46 26 26 71 54 44 26 46 53 40 16 28 69 22 58 24 28 62 15 78 57 65 34 27 54 58 57 28 24 24 72 55 22 20 62 77 58 41 65 42 38 69 33 57 16 54 31 64 67 66 66 79 71 86 29 59 70 40 69 29 28 54 79 84 78 39 30 78 67 66 76 36 20 32 84 57 79 25 84 32 76 44 65 11 56 47 34 24 52 75 71 76 76 86 77 74 41 74 76 61 64 71 71 64 74 26 65 58 75 83 81 71 74 24 71 26 74 28 25 25 61 52 76 82 76 66 76 1 12 9 29 72 31 29 84 65 24 24 68 71 68 62 66 64 37 65 32 39 62 42 73 63 74 38 80 45 64 41 59 41 35 30 72 19 82 24 64 76 18 64 65 64 83 77 70 72 58 46 74 82 74 38 4 66 11 25 56 21 85 71 61 48 78 74 20 22 69 19 74 74 76 57 65 70 33 78 72 44 51 38 34 64 34 32 65 39 77 18 42 36 73 27 24 68 30 28 67 28 25 75 45 39 65 70 68 62 62 33 64 54 59 79 74 30 57 26 6 61 71 33 32 28 38 64 86 36 70 44 6 2 48 39 28 83 24 62 52 41 60 35 44 82 25 48 45 65 66 29 25 49 37 39 62 61 64 31 84 78 76 36 29 12 15 73 9 59 42 34 71 14 41 88 45 60 15 6 25 9 37 32 72 24 31 34 8 56 25 37 78 46 24 37 63 62 66 41 19 72 26 32 52 40 32 47 46 19 65 26 24 24 19 55 44 26 61 40 26 36 63 61 60 58 56 71 56 56 60 41 48 67 66 36 58 53 64 20 72 49 41 45 51 56 27 58 48 58 34 64 12 42 82 24 51 58 44 48 31 46 36 53 22 20 41 29 43 48 24 61 70 67 72 22 18 32 58 35 33 54 32 64 32 40 65 24 33 42 24 53 41 33 25 32 65 23 41 33 25 20 53 27 18 32 46 35 56 49 35 26 33 28 36 61 38 26 42 26 40 56 72 21 44 46 42 22 33 58 80 68 58 60 61 21 58 61 41 15 33 50 48 60 49 21 62 68 65 54 33 30 42 45 64 69 31 56 61 64 32 76 34 61 25 39 13 33 42 26 61 32 80 19 40 41 76 85 61 29 61 5 41 62 53 58 64 62 72 64 69 24 38 41 64 37 54 55 68 39 77 60 40 46 55 55 80 62 62 65 71 63 68 75 34 48 36 56 27 45 14 12 34 18 46 38 44 58 68 38 46 50 42 44 58 32 40 60 40 54 51 65 28 40 35 41 41 62 24 40 48 44 30 46 43 11 66 28 33 46 37 41 26 48 33 60 24 47 42 50 53 18 37 32 81 38 50 55 55 59 11 40 33 33 68 46 41 54 42 44 46 21 55 38 48 48 29 51 49 57 52 50 44 59 58 49 39 50 54 52 33 51 51 48 48 40 49 45 52 52 45 32 49 59 47 55 44 56 39 47 44 51 59 62 52 68 55 64 33 52 46 37 21 57 44 43 32 16 19 35 45 52 48 72 30 62 30 57 60 56 43 24 36 59 43 45 24 24 64 18 37 29 43 71 27 22 42 37 73 24 17 15 54 41 59 55 54 56 84 54 74 63 56 51 55 43 41 41 38 58 21 82 80 41 35 31 1 36 48 48 42 28 11 26 67 82 54 61 67 69 75 70 84 18 71 24 66 84 84 75 70 34 83 68 58 80 45 64 44 79 63 76 80 70 33 56 9 41 64 87 33 66 79 73 81 78 86 75 70 77 70 49 83 9 77 66 50 75 60 47 81 66 84 75 81 75 50 77 59 79 52 81 68 61 58 58 58 63 63 69 74 74 50 15 78 63 77 67 75 81 56 69 70 72 82 72 55 65 66 84 56 74 62 48 62 80 80 70 75 75 65 73 76 48 65 48 75 68 77 68 80 60 82 87 41 75 69 62 82 71 87 46 78 57 55 68 83 15 60 72 60 57 68 74 73 81 78 57 71 85 54 75 76 64 56 72 81 87 65 84 77 30 60 74 66 74 63 74 61 62 83 62 80 65 56 70 81 74 76 69 62 8 65 76 85 71 78 80 74 71 69 45 60 43 69 43 76 54 60 69 56 60 74 74 64 63 75 72 89 65 70 69 72 81 76 64 87 70 72 75 64 74 62 3 65 36 18 43 37 71 63 86 74 61 79 70 80 75 84 80 68 71 88 58 80 86 78 78 78 80 83 87 85 74 70 86 73 16 69 80 69 80 76 82 77 78 76 78 86 66 72 76 56 88 70 50 60 20 75 84 50 45 45 70 67 45 42 64 64 42 64 27 56 60 68 69 50 64 84 73 77 65 65 61 77 65 62 70 45 26 84 60 54 78 44 45 45 81 52 51 50 49 45 35 45 61 25 75 62 40 56 62 67 62 81 45 72 64 50 65 62 58 44 72 48 67 64 80 80 80 87 70 50 65 45 75 57 85 53 50 50 69 72 88 67 58 70 66 61 78 55 70 80 72 81 81 70 84 66 76 54 80 88 82 83 77 82 70 81 70 70 77 45 85 70 73 68 86 69 80 88 75 76 67 80 65 64 70 80 71 66 83 79 75 75 80 81 88 84 75 79 77 43 12 68 78 76 50 75 82 64 84 85 83 79 73 72 34 82 81 60 88 56 56 78 75 81 72 85 84 76 76 87 68 75 76 70 78 70 65 78 80 73 80 76 80 82 47 66 47 89 12 77 80 24 75 80 84 83 78 76 85 73 77 80 80 85 88 85 74 65 30 72 58 38 86 1881 18 69 83 84 78 82 68 33 86 70 32 47 77 84 84 66 76 80 87 76 85 84 74 86 83 61 60 67 73 80 67 81 85 70 74 81 84 67 72 74 82 70 80 79 87 69 86 80 67 82 84 80 76 75 79 52 65 80 75 79 70 86 83 77 79 86 78 73 57 74 86 83 59 56 34 84 67 65 74 74 89 66 74 76 72 70 86 70 86 85 89 55 82 70 59 66 64 74 72 75 61 65 75 65 66 75 86 78 54 86 85 79 85 84 84 84 81 77 78 73 85 78 82 32 86 42 80 86 68 89 82 77 80 86 77 80 85 66 78 86 49 75 87 89 62 72 79 77 84 84 86 89 65 83 63 23 77 76 55 82 87 87 73 87 83 72 30 83 26 35 76 78 74 83 43 75 74 39 74 86 72 70 75 87 75 73 69 64 86 88 75 63 73 75 80 75 74 75 83 80 46 71 82 20 70 75 67 76 36 73 80 77 72 60 55 79 31 47 56 43 76 61 70 66 66 89 83 75 70 67 74 60 54 63 83 68 56 72 71 72 75 63 60 75 71 32 71 73 71 71 70 50 60 44 74 74 65 60 61 47 70 70 69 57 45 62 44 75 60 54 68 42 45 55 55 45 68 69 60 55 63 70 54 68 45 60 44 80 68 56 55 75 65 67 50 65 70 75 58 72 70 79 70 62 60 55 40 65 80 75 56 59 54 53 75 70 78 83 65 71 54 51 65 75 83 75 59 48 63 65 60 81 45 53 54 50 53 73 58 74 65 73 76 75 75 65 80 84 72 32 59 36 67 56 63 79 79 70 65 72 69 59 59 74 72 62 66 65 75 62 66 89 84 80 61 58 63 67 79 76 61 67 62 72 76 71 55 70 61 85 29 81 61 64 70 80 78 61 72 66 65 82 71 50 70 81 76 65 75 71 71 61 67 72 68 6 65 80 66 87 77 65 83 67 74 80 65 78 47 54 66 62 67 62 64 64 65 65 64 69 41 86 72 74 67 72 75 59 19 22 62 72 55 55 74 66 55 74 63 60 65 58 62 52 24 78 60 64 82 59 74 71 75 78 85 74 70 45 73 76 65 52 81 45 62 83 58 55 65 2 28 2 56 45 66 76 79 73 78 65 72 86 66 68 74 67 7 76 53 72 34 64 67 65 70 83 76 63 80 42 31 60 67 63 63 49 60 12 80 69 66 31 75 4 3 67 83 83 15 55 35 74 65 75 70 76 62 74 66 76 70 65 72 75 69 71 44 28 76 71 74 77 71 78 69 76 74 68 80 76 65 31 65 74 64 76 81 74 89 62 78 79 68 68 64 74 58 63 71 58 71 68 66 72 62 74 72 70 70 76 68 82 41 84 68 75 61 85 70 60 45 66 83 66 60 60 60 30 25 54 2 54 61 80 A A ' B B ' C C ' D D ' EXPLANATION OF MAP SYMBOLS Contact—Approximately located; dotted where concealed by water Outcrops—Areas of exposed bedrock or closely spaced contiguous bedrock exposures examined in this study FAULTS [Dotted where concealed by water] Overturned conjectural thrust fault—Parallel to regional S 2 foliation in the Shady Rill fault; sawteeth point in direction of dip, bar on upper plate Reverse fault—Parallel to regional S 3 foliation in Dog River fault zone; U, upthrown side; D, downthrown side FOLDS [Arrow, where present, shows direction of plunge] Inferred axial trace of F 1 fold in Dumpling Hill belt (Taconian)—Box shows dip direction of axial surface Inferred axial trace of F 2 fold (Taconian)—Box shows dip direction of axial surface Overturned F 3 syncline in Silurian and rocks (Acadian F 1 ) Overturned F 3 anticline in Silurian and Devonian rocks (Acadian F 1 ) Upright F 4 antiform in Silurian and Devonian rocks (Acadian F 2 ) Upright F 4 synform in Silurian and Devonian rocks (Acadian F 2 ) Strike and dip of axial surface of minor fold Isoclinal F 2 fold parallel to S 2 foliation Inclined Vertical F 3 fold parallel to S 3 foliation Inclined Vertical F 4 fold parallel to S 4 cleavage Inclined Vertical PLANAR FEATURES [Symbols may be combined; point of intersection shows location of measurement. For foliation symbols, see table 1 (in accompanying pamphlet) for regional correlation of deformational fabrics] Strike and dip of bedding—Ball indicates top of beds known from graded beds Inclined Vertical Inclined, overturned Inclined, highly deformed Strike and dip of lamprophyre or diabase dike (Cretaceous) Inclined Vertical Strike and dip of granitic dike (Devonian) Inclined Vertical Strike and dip of quartz vein Inclined Vertical Steeply dipping; dip uncertain Strike and dip of outcrop-scale brittle fault Strike and dip of deformed S 1 or S 2 schistosity in pre-Silurian rocks Strike and dip of dominant foliation in pre-Silurian rocks—Not age specific but largely S 2 , or S 2 overprinted and parallel to S 3 Inclined Vertical Strike and dip of S 3 schistosity or cleavage (Acadian S 1 ) parallel to bedding in Silurian and Devonian rocks Inclined Vertical Strike and dip of S 3 schistosity or cleavage (Acadian S 1 ) Inclined Vertical Strike and dip of S 4 cleavage (Acadian S 2 ) Inclined Vertical Strike and dip of S 5 cleavage (Acadian S 3 ) LINEAR FEATURES [Symbols may be combined; point of intersection shows location of measurement] Bearing and plunge of deformed mineral aggregate lineation in pre-Silurian rocks (L 2 or older) Bearing and plunge of L 2 mineral aggregate lineation or mineral aggregate lineation of uncertain age (L 2 or L 3 ) in the plane of dominant foliation in pre-Silurian rocks Bearing and plunge of L 3 cleavage-bedding intersection lineation, S 2 –S 3 intersection lineation, mineral aggregate lineation, or stretched-pebble lineation Bearing and plunge of L 4 crenulation or intersection lineation—Also occurs as an aligned biotite aggregate lineation or aligned quartz pressure shadows around garnet in the garnet zone Bearing and plunge of F 2 fold axis in pre-Silurian rocks Bearing and plunge of F 3 fold axis Bearing and plunge of F 4 fold axis Bearing and plunge of F 5 fold axis or crenulation Slickensides on brittle fault OTHER FEATURES Abandoned quarry Active quarry Location of conspicuous garnet porphyroblasts in the eastern Waits River Formation Metamorphic isograd (Acadian) Mafic rock localities in the Wrightsville belt—Shows locations where greenstone and (or) metadiabase of uncertain origin (volcanic or intrusive) were seen but not mapped as separate units Greenstone and metadiabase sample locality from Twelker (2004) Greenstone Greenstone and metadiabase Metadiabase Spring Four fossil localities in the Waits River Formation—No. 7 locality from Cady (1950); three U.S. National Museum localities from Hueber and others (1990) Location of irregularly shaped quartz vein Site of photograph—Tip of arrow at point of observation; number keyed to figure in explanatory pamphlet DESCRIPTION OF MAP UNITS [Major minerals listed in order of increasing abundance] IGNEOUS AND METASOMATIC ROCKS Lamprophyre or diabase dike (Cretaceous)—Aphanitic, very dark gray to black, brown- and rusty-weathering lamprophyre or diabase dikes; location shown by strike and dip symbol. Dikes range in thickness from 0.4 to 2 m and locally contain phenocrysts of biotite, amphibole, pyroxene, and olivine. Dikes may show zoning and chilled margins and locally contain amygdules filled with dolomite or calcite. Wall rocks generally contain subparallel joint sets. Dikes are unfoliated but may be jointed Quartz vein (Devonian)—Map-scale quartz veins locally measure as much as 15 to 20 m thick, north of Martin Brook in Williamstown and on the northern side of Irish Hill in Berlin. Other mapped veins are approximately 3 m thick or less, and their sizes are exaggerated on the map to show the locations. Conspicuous outcrop-scale tabular quartz veins are shown by strike and dip symbols and range in thickness from 3 cm to 3 m. Veins contain accessory muscovite and ankerite. Large, irregular quartz veins as much as several meters across are shown with point symbols. Smaller, irregularly shaped quartz veins are ubiquitous and have not been mapped separately Granitic dike (Devonian)—Fine- to medium-grained, moderately to weakly foliated or unfoliated, very light gray to white- or tan-weathering trondhjemite, granodiorite, or muscovite-biotite granitic dikes. The rock contains variable amounts of muscovite, biotite, K-feldspar, quartz, and plagioclase. Feldspar compositions primarily include microcline and oligoclase (Chayes, 1952; Cady, 1956; Murthy, 1957). Rocks contain accessory carbonate, sphene, zircon, epidote, clinozoisite, chlorite, and pyrite. Thin dikes and the margins of thick dikes and sills exhibit S 3 foliation (Acadian S 1 ); the interiors of large bodies may be unfoliated. Dikes occur primarily in two places: (1) near the village of Adamant where Cady (1956) identified the type locality of the Adamant Granite in Calais and (2) along strike to the southwest near Crosstown Road in Berlin. Abandoned quarries are found in both areas. The dikes cut bedding and are generally parallel to the steep S 3 foliation (Acadian S 1 ). Outcrop-scale dikes (0.25 to 3 m thick) occur throughout the eastern part of the area and are shown by strike and dip symbols. Larger map-scale dikes are as much as several hundred meters thick. Thin dikes are locally trondhjemitic to granodioritic, are locally porphyritic with microcline phenocrysts ≤0.5 cm, and contain secondary pyrite porphyroblasts ≤0.5 cm. Country rock may be brecciated along the margins of the dikes ROCKS OF THE CONNECTICUT VALLEY-GASPÉ SYNCLINORIUM Gile Mountain Formation (Devonian) Phyllite and quartzite—Interbedded dark-gray to silvery-gray quartz- muscovite phyllite or fine-grained schist and micaceous or feldspathic quartzite, locally sulfidic and rusty weathering. Quartzite consists approximately of 80 percent quartz, 10 percent plagioclase and biotite, and accessory muscovite, chlorite, and garnet. Graded beds, locally present (10–30 cm thick), most of which are overturned to the southeast. The schist generally contains less than 20 percent biotite, chlorite, and plagioclase and accessory porphyroblasts of garnet. Accessory minerals include pyrite, rutile, ilmenite, hematite, magnetite, zircon, apatite, tourmaline, and graphite Calcareous phyllite—Dark-gray, dark-brown-weathering calcite-chlorite- plagioclase-quartz-muscovite phyllite occurs in layers, 30 to 40 cm thick within Dgm. Rock is similar to thin, unmapped layers within the Waits River Formation. The size of the unit is exaggerated on the map to show its location Limestone—Bluish-gray, brown-weathering, impure, siliceous muscovite- quartz-calcite limestone or marble; occurs as a single 50-cm-thick layer within Dgm along McGlynn Road (name not shown on map) in Williamstown. Rock is similar to limestone within the Waits River Formation. The size of the unit is exaggerated on the map to show its location Waits River Formation (Devonian and Silurian)—Units not necessarily in stratigraphic order Thickly bedded limestone and phyllite—Interbedded dark-gray to silvery-gray, locally sulfidic and rusty-weathering, chlorite-plagioclase- quartz-muscovite phyllite, slate, or schist and brown-weathering, bluish-gray to gray, impure, siliceous limestone or marble. The phyllite contains less than 10 percent chlorite and plagioclase and accessory biotite and garnet porphyroblasts in the garnet zone and rare biotite porphyroblasts in the biotite zone. Quartz may occur as millimeter-scale clasts interpreted as detrital, matrix-supported grains. Generally the pelites are slaty to phyllitic in the biotite zone and schistose in the garnet zone. Other accessory minerals in the pelites include pyrite, calcite, rutile, ilmenite, hematite, zircon, monazite, apatite, tourmaline, graphite, xenotime, and possible thorite. The limestones contain trace to 5 percent muscovite, 20 to 40 percent quartz, and 60 to 80 percent calcite with accessory plagioclase, pyrite, opaques, graphite, tourmaline, and apatite. Limestone beds generally measure 1.0 to 5.0 m thick and locally measure as much as 9.0 m thick. Phyllite beds generally measure 0.2 to 1.3 m thick. Contains rare, thin beds (≤20 cm) of light-gray quartzite similar to DSwq. Bedding is clearly visible as the contacts between limestone and phyllite. Bedding within the phyllite is difficult to see but is locally indicated by concentrations of sulfides, the most readily identifiable of which is pyrite. Map unit is similar in composition to DSwl 1 and DSwl 2 , but bedding in the phyllites and especially in the limestones is appreciably thicker in DSwt Thinly bedded limestone and phyllite—Interbedded dark-gray to silvery-gray, locally sulfidic and rusty-weathering, chlorite-plagioclase- quartz-muscovite phyllite, slate, or schist and brown-weathering, bluish-gray, impure, siliceous limestone or marble. The phyllite contains accessory biotite and garnet porphyroblasts in the garnet zone and rare biotite porphyroblasts in the biotite zone. Composition of limestones and phyllites similar to DSwt. Contains rare, thin beds (≤20 cm) of light-gray quartzite similar to DSwq. Limestone beds generally measure 0.2 to 3.0 m thick and locally measure as much as 5.0 m thick. Phyllite beds generally measure 0.2 to 0.5 m thick. Bedding is clearly visible as the contacts between limestone and phyllite. Bedding within the phyllite is difficult to see but is locally indicated by concentrations of rusty-weathering pyrite. DSwl 1 occurs at the base and DSwl 2 occurs at the top of the Waits River Formation, but the rocks are lithologically similar Phyllite—Dark-gray to silvery-gray, locally sulfidic and rusty-weathering chlorite-quartz-muscovite slate, phyllite, slaty phyllite, or fine-grained schist. Contains accessory biotite and garnet porphyroblasts in the garnet zone and rare biotite porphyroblasts in the biotite zone. Contains less than 10 percent plagioclase. Accessory minerals include pyrite, calcite, rutile, ilmenite, zircon, monazite, apatite, tourmaline, graphite, and xenotime. Bedding is difficult to see but is locally indicated by concentrations of sulfides. Where visible, bedding is generally 0.2 to 0.5 m thick. DSw 1 occurs within DSwl 1 , and DSw 2 generally occurs between DSwl 2 and DSwt. Rocks mapped simply as “DSw” are interpreted as lenses of phyllite due to facies changes at several places within the Waits River Formation. Lithologically, these units are similar to the phyllite in the DSwt, DSwl 1 , and DSwl 2 units Garnetiferous phyllite—Dark-gray, non-rusty-weathering garnet-chlorite- quartz-muscovite phyllite with distinctive, abundant, small (0.1–2.0 mm), euhedral garnet porphyroblasts or chlorite pseudomorphs after garnet. Contains less than 10 percent plagioclase. Accessory minerals include pyrite, calcite, rutile, ilmenite, zircon, monazite, apatite, tourmaline, graphite, and xenotime. Unit occurs within DSwl 1 . Unit marks the western limit of the Acadian garnet isograd Quartzite—Light-gray, locally rusty-weathering and sulfidic, micaceous to feldspathic to calcareous quartzite. Rock contains 75 percent or more quartz, and 5 to 10 percent muscovite, plagioclase, and (or) calcite. Accessory minerals include pyrite, graphite, tourmaline, and zircon or monazite. The quartzite consists of multiple or individual beds, 0.3 to 3 m thick. The quartzite is locally interlayered with dark-gray quartz-muscovite phyllite. The size of the unit is exaggerated on the map to show its location. Rare, thin, unmapped quartzite also occurs within DSwt, DSwl 1 , and DSwl 2 Northfield Formation (Devonian? and Silurian) Phyllite—Dark-gray, locally rusty-weathering and sulfidic, quartz-muscovite phyllite or slate. Bedding in the phyllite, although rarely visible in natural outcrops and more visible in roadcuts, generally ranges from 10 to 30 cm thick. Thin, micaceous quartzite and brown-weathering calcareous phyllite beds ≤20 cm thick locally occur in the Northfield Formation and define bedding, where present. Thin (≤10 cm), impure limestone beds are very rare but increase in abundance at the eastern contact with the Waits River Formation. The contact with the Waits River Formation is mapped on the first occurrence of abundant interbedded limestone Conglomerate—Dark-gray, matrix-supported conglomerate. Poorly exposed at a single outcrop along the Dog River in Berlin, near the base of the Northfield Formation. Matrix consists of dark-gray phyllite similar to the phyllite of the Northfield Formation (DSn). Clasts consist of tabular, tectonically elongated rock fragments of light-gray to white ankerite-spotted phyllite and quartzite measuring as much as approximately 10 cm thick by 50 cm long. Conglomerate is intraformational within the Northfield Formation near its base and approximately 2 to 3 m thick. The size of the unit is exaggerated on the map to show its location Shaw Mountain Formation (Silurian) Ankeritic greenstone and green schist—A heterogeneous unit of interlayered rocks consisting largely of ankeritic greenstone and green calcareous quartz-chlorite-albite schist. Greenstone is a light- to dark-green, actinolite-epidote-quartz-chlorite-albite rock, locally with conspicuous epidote as laminae and elliptical pods flattened parallel to the dominant foliation. Greenstone locally contains albite porphyroblasts and (or) plagioclase phenocrysts. Contains interlayered green and gray phyllite and gray to dark-gray carbonaceous phyllite; gray to gray-green, punky-weathering, calcareous quartz-albite-chlorite- calcite (or ankerite) schist or granofels; silvery-gray, cream-weathering muscovite-quartz-plagioclase schist and granofels; pale-gray to tan, cream- to tan-weathering, ankerite-spotted micaceous quartzite and small-pebble conglomerate. Contains conglomerate lenses mapped separately as Ss. The contact with the Cram Hill Formation is gradational and marked by interlayered gray to dark-gray carbonaceous phyllite within Ssg near the contact. The contact with the Northfield Formation is sharp. Unit interpreted as interlayered metavolcanic and volcaniclastic rock Conglomerate—Quartz-pebble and quartz-cobble conglomerate. Slightly to very rusty weathering and friable conglomerate composed dominantly of rounded pebbles and cobbles of medium- to coarse-grained vein quartz and rare metamorphic rock fragments consisting of elongate pieces of gray granofels. Contains interlayered green and gray phyllite and punky-weathering, calcareous quartz-albite-chlorite-calcite schist or granofels. Clast-supported zones in the conglomerate locally grade into phyllite or granofels. Locally very friable and sulfidic with abundant disarticulated quartz veins. Occurs as thin, discontinuous lenses, as much as 5 m thick, entirely within Ssg. Quartz pebbles are relatively undeformed in the northeastern part of the field area and are unlike the stretched and elongated clasts in the conglomerate of the Northfield Formation (DSnc) in the Dog River fault zone to the south ROCKS OF PRE-SILURIAN AGE Metadiabase and greenstone dikes or sills (Silurian? to Ordovician?)—Grayish-green to green, fine- to medium-grained, massive, weakly foliated greenstone and coarse-grained, massive, weakly foliated metadiabase. Due to the massive structure, outcrops weather to rounded bulbous shapes. Major minerals include quartz, chlorite, epidote, actinolite, and plagioclase. Locally contains plagioclase phenocrysts and relict diabase texture where plagioclase content exceeds and encloses semi-rectangular masses of epidote-actinolite that probably originated as pyroxene. Fresh surfaces locally effervesce in HCl due to the presence of secondary calcite. The intrusions are approximately 0.3 to 3 m wide. Relict chilled margins are common on the thicker intrusions. Contacts with the adjacent rocks are usually concordant, subparallel to the dominant S 2 foliation but locally exhibit low- to high-angle discordance with the dominant S 2 foliation. The dikes predate the S 3 foliation. The dikes are discontinuous, and individual bodies could not be traced very far along strike. Dikes or sills occur as fine- to medium-grained greenstone both with and without diabase texture. Whole-rock geochemistry from samples in the Montpelier quadrangle shows basaltic compositions (Twelker, 2004). These dikes were observed only in the Wrightsville belt. The intrusions are shown on the map as small elongate bodies. The size of the dikes is exaggerated on the map to show the location. Point symbols show locations on the map where greenstone and (or) metadiabase of uncertain origin (volcanic or intrusive) were seen but not mapped separately Cram Hill Formation (Ordovician)—Contains greenstone layers and metadiabase or greenstone dikes and sills Carbonaceous phyllite—Gray to dark-gray or black carbonaceous phyllite locally interlayered with silvery-gray phyllite, feldspathic quartzite, and greenstone. Rusty-weathering, gray to dark-gray or black chlorite- plagioclase-quartz-muscovite phyllite that is locally carbonaceous (±graphite). Carbonaceous phyllite is locally pyritiferous. Locally interlayered with silvery-gray and grayish-green phyllite and massive, gray, granular feldspathic quartzite (usually boudinaged). Rare, pearly-white-weathering quartz-feldspar granofels interpreted as metatuffs occur in the northeastern part of the map on the eastern side of this formation. Punky-weathering, silvery-green ankerite-calcite- chlorite-albite schist to ankeritic greenstone with calcite-ankerite porphyroblasts occurs locally in the eastern part of the Cram Hill Formation; because this lithology is similar to highly weathered ankeritic greenstones in the Cram Hill and Moretown Formations, we place the greenstone in the pre-Silurian section and not in the Shaw Mountain Formation as did Cady (1956) Quartzite—Massive to well-foliated, light-gray to dark-gray or gray banded quartzite; may be feldspathic or micaceous due to the presence of plagioclase and (or) muscovite. Contains trace carbonate, graphite, apatite, tourmaline, and opaques. Locally contains rusty-weathering porphyroblasts of ankerite or octahedra of magnetite. Occurs as disarticulated lenses or boudins or as layers as much as several meters thick. Thin, unmapped similar quartzites occur throughout the Cram Hill Formation Phyllite and granofels with coticule—Black-weathering, gray and green chlorite-plagioclase-quartz-muscovite phyllite and granofels with thin millimeter-scale ribbons of disarticulated coticule (fine-grained quartz-spessartine rock); contains greenstone layers, some with phenocrysts of plagioclase. Coticule layers locally form rootless isoclinal folds that intersect on foliation surfaces as downdip lineations parallel to these fold axes. Thin coticule layers stand out in relief as resistant ridges Interlayered phyllite, quartzite, and granofels—Interlayered grayish-green to silvery-gray chlorite-plagioclase-quartz-muscovite phyllite with porphyroblasts of magnetite; micaceous quartzite with porphyroblasts of ankerite; grayish-green granofels; dark-gray phyllite; rare dark-gray to black carbonaceous phyllite; minor quartz-pebble conglomerate; and greenstone. This unit is transitional in composition between the Ochr unit of the Cram Hill and the Om unit of the Moretown Formation Moretown Formation in the Wrightsville belt (Ordovician and Cambrian)—Contains greenstone layers and metadiabase and greenstone dikes or sills; locally mapped separately or shown with symbols Phyllite, granofels, and “pinstripe” granofels—Interlayered light-green and silvery-green to grayish-green chlorite-plagioclase-quartz-muscovite phyllite, schist, and chlorite-muscovite-plagioclase-quartz granofels and “pinstripe” granofels; locally contains small-pebble conglomerate similar to Omq. Accessory minerals include biotite, opaques, magnetite, calcite, apatite, and tourmaline. In the central part of the map between Montpelier and Middlesex, the unit is studded with magnetite. Locally contains massive, gray to light-gray, granular quartzites similar to Omq. The characteristic “pinstripe” fabric is defined by alternating millimeter-scale layers of albite-quartz and chlorite-muscovite. Punky-brown-weathering, silvery-green to light-green calcite-chlorite- plagioclase-quartz schist and granofels with porphyroblasts of calcite and muscovite (≤2 mm) are locally present in the eastern part of the formation. Contains rare, dark-gray to black, rusty-weathering carbonaceous quartz-muscovite phyllite (Ombp) mapped separately at one place along the Dog River Feldspathic quartzite and small-pebble conglomerate—Gray to grayish-green, fine- to medium-grained micaceous or feldspathic quartzite and muscovite-chlorite-plagioclase-quartz small-pebble conglomerate with matrix-supported clasts generally as much as 0.5 mm, and rarely as much as 1 cm, composed chiefly of feldspar and blue quartz. Occurs as layers, 0.5 to 2 m thick within Om Greenstone—Green to grayish-green, fine- to medium-grained, weakly to moderately foliated, locally layered actinolite-quartz-sphene-calcite- chlorite-plagioclase gneiss or “greenstone” and locally massive, unfoliated to weakly foliated, green to grayish-green quartz-sphene- calcite-amphibole-chlorite-plagioclase greenstone. Massive rocks weather to rounded bulbous outcrops. The greenstones are interpreted as metamorphosed mafic extrusive volcanic to volcaniclastic rocks or possibly intrusive rocks. May contain thin (<20 cm) metadiabase layers that resemble metadiabase dikes mapped separately (SOdg). In the field, it is not always possible to separate the greenstone from the metadiabase or see features that would conclusively demonstrate extrusive versus intrusive origin, and for this reason we map Omg simply as greenstone. Greenstones contain more calcite and chlorite and are more strongly foliated than metadiabases. Where present, plagioclase clasts, interpreted as relict phenocrysts, locally increase in abundance away from the contacts with surrounding rocks. Fresh surfaces weakly effervesce in dilute HCl due to the presence of secondary calcite. Trace element geochemistry shows the sampled greenstones have tholeiitic basalt signatures (Twelker, 2004). These mafic rocks occur only in the Wrightsville belt Interlayered green and dark-gray phyllite—Interlayered gray and green phyllite; quartzite; rusty-weathering, dark-gray to black carbonaceous phyllite; and grayish-green granofels and “pinstripe” granofels; similar to Omsr. Grayish-green rocks are similar to Om, and carbonaceous rocks are similar to Omdh of the adjacent Dumpling Hill belt Moretown Formation in the Dumpling Hill belt (Ordovician and Cambrian)—Does not contain greenstone layers or metadiabase or greenstone dikes or sills Interlayered green and dark-gray phyllite—Interlayered gray and green phyllite; quartzite; rusty-weathering, dark-gray to black carbonaceous phyllite; and granofels; similar to Omw of the adjacent Wrightsville belt. Grayish-green rocks are similar to Ompb in this belt and Om in the adjacent Wrightsville belt, and carbonaceous rocks are similar to Omdh in this belt and Ombp in the Wrightsville belt Phyllite, granofels, and “pinstripe” granofels—Interlayered green phyllite; granofels; green “pinstripe” granofels; quartzite; and quartz-pebble conglomerate; similar to Om in the Wrightsville belt Carbonaceous phyllite and quartzite—Dark- to medium-gray and black phyllite; minor granofels; laminated, tan-weathering quartzite; vitreous quartzite; and rare quartz-pebble conglomerate. Dark-gray and black phyllite is carbonaceous, rusty weathering, and locally pyritiferous. Bedding and a relict S 1 layer-parallel schistosity are preserved in more massive granofels and quartzites, although they are commonly transposed in the plane of S 2 . Bedding and subparallel S 1 at high angles to the S 2 foliation is exposed near the summit of Dumpling Hill where F 2 and later folds plunge to the north. A typical section is exposed on the eastern flank of Dumpling Hill, southwest of Worcester where 1.0- to 1.5-m-thick beds of dark-gray phyllite are interbedded with tan-weathering, white- and gray-laminated quartzite. A 1.5-m-thick bed of quartz-pebble conglomerate occurs near the summit near the contact with green granofels. Quartzite-rich horizons in this unit compose topographically high areas such as Dumpling Hill Dq Dg Dgm Dgmcp Dgml DSwt DSwl 1 DSwl 2 DSwg DSwq DSn DSnc Ssg Ss SOdg Ochr Ochq Ochc Ochi Om Ombp Omq Omg Omw Omsr Ompb Omdh DSw DSw 1 DSw 2 CORRELATION OF MAP UNITS Dg Dq IGNEOUS AND METASOMATIC ROCKS ROCKS OF THE CONNECTICUT VALLEY-GASPÉ SYNCLINORIUM DSn DSw 2 DSwg DSw DSwl 1 DSwq DSwt Dgm Dgmcp Dgml DSnc DSwl 2 DSw DSw 1 DSwt Ss Ssg SOdg Unconformity and Dog River fault zone Richardson Memorial Contact Metadiabase and greenstone dikes or sills Om Omg Omq Omw Ompb Omdh Ombp Omsr Wrightsville belt Dumpling Hill belt Lamprophyre or diabase dike Quartz vein Granitic dike Ochc Ochq Ochr Ochi S h a d y R i l l f a u l t CRETACEOUS SILURIAN DEVONIAN DEVONIAN AND SILURIAN SILURIAN(?) TO ORDOVICIAN(?) ORDOVICIAN AND CAMBRIAN ORDOVICIAN Waits River Formation Northfield Formation Cram Hill Formation Moretown Formation Gile Mountain Formation Shaw Mountain Formation ROCKS OF PRE-SILURIAN AGE Om Om DSwt DSwt DSwt DSwt DSwt DSwl 1 DSwl 1 DSwl 1 DSwt Omdh Omdh Omsr DSwt DSwt Omw Omw Dgm DSn DSn DSw 2 DSwl 2 DSn DSn DSn DSw 1 DSw 1 DSw 2 DSw 2 DSw 2 Ompb DSw 2 DSw 2 Ochi Ochi Ompb Ochr Ochr Ochr Ochr Ochr Ochi Ochi Dg Dg Dg DSw Dg Dg Ompb Omg Omg Omg Omg Omg Omg Ombp Ochq Ochq Omq DSw Ompb Omsr Om Ssg Ssg Ochr Ssg Ss Ss Ochq Ochq DSnc Omq Omq DSwt DSwq Dg Dq Dg Ochc Ochc SOdg Dg DSwt Dg Dg Dg Dg Dg Dg Dg Dg Dg Dg Dg Dg Dg Dg Dg DSw DSwg DSwq Dq DSwl 1 DSwl 1 DSwl 1 DSwl 1 DSwl 1 DSwl 1 DSwl 1 DSwl 1 DSwq Dgml Dgmcp Dg Dgmcp Ompb Omg Omg SOdg Dq SOdg SOdg SOdg SOdg Ompb SOdg DSwt DSw 2 DSw 2 DSwg DSw DSn Om Om Ompb DSwl 1 DSwt DSwg DSwg DSwg DSwg STOWE ROXBURY PLAINFIELD MIDDLESEX WOODBURY BARRE EAST NORTHFIELD BROOKFIELD MONTPELIER BARRE WEST WASHINGTON MOUNT WORCESTER Index to 7.5-minute topographic maps BEDROCK GEOLOGIC MAP OF THE MONTPELIER AND BARRE WEST QUADRANGLES, WASHINGTON AND ORANGE COUNTIES, VERMONT By Gregory J. Walsh, 1 Jonathan Kim, 2 Marjorie H. Gale, 2 and Sarah M. King 2 1 U.S. Geological Survey, Montpelier, VT 05601. 2 Vermont Geological Survey, Waterbury, VT 05671. 2010 U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Prepared in Cooperation with the VERMONT GEOLOGICAL SURVEY Geology mapped from 2002–05 Digital compilation by Walsh and Kim Base from U.S. Geological Survey Montpelier 1999; Barre West 1978 (photorevised 1988) Transverse Mercator projection. 1927 North American Datum 10,000-foot grid ticks based on Vermont coordinate system 1,000-meter Universal Transverse Mercator grid ticks, zone 18 SCIENTIFIC INVESTIGATIONS MAP 3111 Explanatory pamphlet accompanies map MAP LOCATION VERMONT INDEX TO MAPPING Kim, Gale, King, and Walsh Walsh This map is available for sale by U.S. Geological Survey, Information Services, Box 25286, Denver Federal Center, Denver, CO 80225 For product and ordering information: World Wide Web: http://www.usgs.gov; Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government CONTOUR INTERVAL 20 FEET 7000 FEET 1000 1000 0 2000 3000 4000 5000 6000 .5 1 KILOMETER 1 0 SCALE 1:24 000 1/ 2 1 0 1 MILE MAGNETIC NORTH APPROXIMATE MEAN DECLINATION, 2010 TRUE NORTH 15° DSw 2 DSw 2 DSw 2 Dgm DSw DSw DSw 1 DSw 1 DSwg DSwl 2 DSwl 1 DSwl 1 DSwl 1 DSwt DSwl 1 DSwl 1 DSwl 1 DSwl 1 DSwt A DSn Dg Dg Irish Hill INTERSTATE 89 STEVENS BRANCH 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 FEET 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 SU R F A C E SU RF AC E NO VERTICAL EXAGGERATION 1000 feet = 305 meters Surficial deposits not shown FEET A ' S 3 (Acadian S 1 ) S 0 in Silurian and Devonian rocks WRIGHTSVILLE BELT DSn DSw 2 DSw 2 Om Om Om Ombp Omg Ochr DSwt DSwt DSwl 1 DSwg DSwl 1 Omg Omg Omg Ochq STATE ROUTE 62 STATE ROUTE 62 STEVENS BRANCH DOG RIVER INTERSTATE 89 Omg B 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 FEET 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 FEET B ' NO VERTICAL EXAGGERATION 1000 feet = 305 meters Surficial deposits not shown D O G RIV E R F A U L T Z O N E SURFACE SUR F A C E S 3 (Acadian S 1 ) S 0 in Silurian and Devonian rocks S 2 in pre-Silurian rocks (pre-Acadian) WRIGHTSVILLE BELT DSwt DSw 2 DSwl 1 DSwg DSwl 1 Om DSn Om Ochc Ochr Ochi SHADY RILL FAULT Ompb Omdh NORTH BRANCH DOG RIVER FAULT ZONE C 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 FEET 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 4000 4000 FEET C ' NO VERTICAL EXAGGERATION 1000 feet = 305 meters Surficial deposits not shown SUR FA CE SURFAC E S 3 (Acadian S 1 ) S 0 in Silurian and Devonian rocks S 2 in pre-Silurian rocks (pre-Acadian) DSn DSwl 1 DSwl 1 Dg Ssg Om Om SHADY RILL FAULT Omdh Omdh Omsr Omsr Omw Dg Dg DSwt Ochi Ochr DUMPLING HILL BELT DUMPLING HILL BELT WRIGHTSVILLE BELT Ompb Om S 3 (Acadian S 1 ) S 0 in Silurian and Devonian rocks S 2 in pre-Silurian rocks (pre-Acadian) S 1 in pre-Silurian rocks (pre-Acadian) NORTH BRANCH Dumpling Hill Long Meadow Hill Adamant Richardson Memorial Contact D 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 FEET 2000 SEA LEVEL 1000 1000 3000 4000 2000 3000 FEET D ' NO VERTICAL EXAGGERATION 1000 feet = 305 meters Surficial deposits not shown SURFACE SU RFA CE RICHARDSON MEMORIAL CONTACT WRIGHTSVILLE BELT DUMPLING HILL BELT CONNECTICUT VALLEY-GASPÉ SYNCLINORIUM DOG RIVER FAULT ZONE SH A D Y R I L L F A UL T 44°07’30” 44°15’ 44°22’30” 72°30’ 72°37’30” 5 KILOMETERS 0 Figure 1.—Simplified tectonic map showing distribution of greenstone and (or) metadiabase mafic rocks (black circles) in the Wrightsville belt.
